System and method for linked slot-level burn-in

ABSTRACT

Some embodiments of the invention provide a burn-in system that links a Burn-In Board (BIB) Loader/Unloader (BLU) to a burn-in chamber rack using a BIB transfer module. The BIB transfer module is capable of transferring a BIB between the BLU and the bum-in chamber rack by moving the BIB in at least two perpendicular directions while minimizing the physical footprint required by the BIB transfer module. The system supports slot level burn-in of components as opposed to batch level burn-in because the burn-in chamber rack may begin the bum-in process as soon as a BIB is delivered to an individual chamber slot in the burn-in chamber rack. The BIB transfer module may easily be detached and separated from the BLU and the burn-in chamber rack without affecting the continuing operation of the BLU and the bum-in chamber rack. Other embodiments are described and claimed.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This disclosure relates in general to burn-in systems and methods, andmore particularly, to a system and method for linked, slot-level burn-inof components.

2. Description of the Related Art

The term “burn-in” refers to an electrical stress test that employsvoltage and temperature to accelerate the electrical failure of adevice. Burn-in essentially simulates the operating life of the device,since the electrical excitation applied during burn-in may mirror theworst-case bias that the device will be subjected to in the course ofits useable life. Depending on the bum-in duration used, the reliabilityinformation obtained may pertain to the device's early life or itswear-out. Burn-in may be used as a reliability monitor or as aproduction screen to weed out potential infant mortalities from the lot.

Burn-in is typically done at an elevated temperature while electricalexcitation is applied to the sample devices. The burn-in process isfacilitated by using burn-in boards (BIBs). A number of sample devicesmay be placed on each BIB, and the BIBs are then inserted into a burn-inchamber that supplies the necessary voltages to the samples whilemaintaining the chamber at the desired temperature. The burn-in chamberincludes a number of chamber slots, each slot configured to accommodateone BIB and the components that it holds. The electrical bias applied tothe devices may either be static or dynamic, depending on the failuremechanism that is being accelerated during the burn-in process.

Some conventional component burn-in systems are not automated. That is,operators must manually load the BIBs with devices, place the BIBs inthe slots of the burn-in chamber, remove the BIBs, remove the bakeddevices from the BIBs, and then repeat the process for the other unbakeddevices.

Other conventional burn-in systems are partially automated. For example,a conventional piece of automated equipment that is often used inburn-in systems is known as a Burn-in board Loader/Unloader (BLU). TheBLU may be used to mechanically load devices from a JEDEC tray to a BIBor vice versa. The term “JEDEC tray” refers to a component packagingtray that is standardized across the industry for each type of devicepackage, i.e., Pin Grid Array packages (PGAs), Ball Grid Array packages(BGAs), Ceramic Quad Fine Pitch packages (CQFPs), etc. However, once thecomponents are transferred to the BIBs, the operators must stillmanually transfer the BIBs to the other units of the burn-in system, forexample, the burn-in chamber. Since the BLUs and burn-in chambers of aconventional burn-in system are typically spread widely throughout aroom, trolleys or carts are used to manually transport a large number oftrays or BIBs to, from, or between the BLUs and burn-in chambers.

The conventional systems and methods of burn-in described above aremanually intensive, costly, and require large physical spaces.Conventional burn-in systems are also susceptible to “staging”, meaningthat because the system components are not linked, the operators willtypically wait until a trolley or cart is completely filled with BIBsbefore moving the BIBs to the burn-in chamber. Embodiments of theinvention address these and other disadvantages inherent in theabove-described conventional burn-in systems.

BRIEF DESCRIPTION OF THE DRAWINGS

Some exemplary embodiments of the invention will be explained below withreference to the following diagrams, where like reference numerals referto like elements throughout.

FIG. 1 is a block diagram that conceptually illustrates some transferprocesses between components of a burn-in system according to someembodiments of the invention.

FIG. 2 is a top-view diagram that illustrates the physical footprint andphysical relationship between components of the linked burn-in system ofFIG. 1, as well as further details of the movement of a JEDEC trays andBIBs within the burn-in system.

FIGS. 3A and 3B are perspective diagrams further illustrating an exampleBIB transfer module 120 from the burn-in system of FIG. 2.

FIGS. 4A, 4B, and 4C are perspective diagrams further illustrating theBIB transfer mechanism of FIGS. 3A and 3B.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, exemplary embodiments of theinvention will be described with reference to the FIGURES. It should berecognized that the exemplary embodiments described below are notintended to be a comprehensive list of all embodiments of the invention.Rather, the embodiments are described for illustrative purposes so thatothers of skill in the art may easily understand the inventive conceptsthat may be characteristic of any number of specific embodiments of theinvention.

Embodiments of the invention provide a burn-in system that significantlyimproves burn-in chamber utilization while reducing the physicalfootprint. According to some embodiments of the invention, a burn-insystem includes a BLU that quickly transfers components to/from standardJEDEC trays and BIBs. The system further includes at least one BIBtransfer module that may automatically load BIBs with unbaked componentsinto a chamber slot of the burn-in chamber. The BIB transfer module mayalso automatically unload the BIBs with baked components and return themto the BLU, where they are subsequently unloaded and returned to a JEDECtray.

These and other features and advantages of embodiments of the inventionwill be explained in further detail in the discussion that follows.

FIG. 1 is a block diagram that conceptually illustrates some transferprocesses between components of a linked module burn-in system 100according to some embodiments of the invention. The burn-in system 100includes a BLU 110. The BLU 110 may transfer components from astandardized JEDEC tray 114 to a BIB 112 and vice versa. The burn-insystem 100 also includes two BIB transfer modules 120. Each of the BIBtransfer modules 120 transfers BIBs between the BLU 110 and acorresponding burn-in rack 140 that forms part of a burn-in chamber 130.Each of the burn-in racks 140 may have a number of chamber slots (notshown). Each chamber slot is structured to hold one BIB, along with thecomponents that the BIB carries, during a burn-in process. The chamberslots are typically stacked vertically with respect to each other.Consequently, the BIB transfer modules 120 have the capability to moveBIBs in the vertical (z-axis) direction. The mechanism that the BIBtransfer modules 120 uses to accomplish this vertical movement of theBIBs will be explained in further detail below in the description of theBIB transfer module 120.

FIG. 2 is a top-view block diagram that illustrates the physicalfootprint and physical relationship between components of the linkedmodule burn-in system 100 of FIG. 1, as well as further details of themovement of a JEDEC tray 114 and a BIB 112 within the burn-in system100. It should be noted that the components of the burn-in system 100illustrated in FIG. 2 are not necessarily drawn to scale. Furthermore,the arrows illustrated in FIG. 2, while generally indicative of thepaths that the BIBs follow within the system 100, should not beconsidered to represent exactly the position of the BIBs within thesystem 100.

Referring to FIG. 2, two BIB transfer modules 120 are shown detachablylinked to a standalone BLU 110 and a burn-in chamber 130 that includestwo burn-in racks 140. Unburned components are loaded in the BLU 110using a JEDEC tray 114. The BLU 110 transfers the unburned components toa BIB 112. The BLU 110 may route the BIB 112 to one of the two BIBtransfer modules 120 that are linked to the BLU 110. Once the BIB 112has been transferred to the BIB transfer module 120, the BIB transfermodule transfers the BIB 112 to a chamber slot of the correspondingburn-in rack 140 in the burn-in chamber 130. This may require the BIBtransfer module 120 to move the BIB 112 in the vertical (z-axis)direction. After the burn-in process is complete, the BIB 112 thatcontains the burned components is removed from the chamber slot by theBIB transfer module 120 and returned to the BLU 110. The BLU 110 unloadsthe burned components from the BIB 112 to a JEDEC tray 114 which maythen be removed from the BLU.

During the time period that a burn-in is being performed on one BIB 112,there may be other BIBs 112 in the system 100 that are in differentstages of their own burn-in process. For example, other BIBs 112 may bein other chamber slots in the burn-in racks 140. Other BIBs 112 may alsobe present in the BLU 110, where the components are loaded prior toburn-in within the chamber slot and unloaded after burn-in in thechamber slot.

The embodiments of the invention illustrated in FIG. 2 also facilitateparallel processing because as soon as one BIB 112 with unburnedcomponents is delivered to one of the BIB transfer modules 120 by theBLU 110, the BLU 110 may immediately retrieve another BIB 112 withunburned components and deliver that BIB to the other BIB transfermodule 120. The BLU 110 may also retrieve BIBs 112 with burnedcomponents from each of the BIB transfer modules 120 in the samefashion.

Consequently, the above-described embodiments of the invention supportslot-level burn-in of components versus batch-level burn-in ofcomponents. In other words, because each chamber slot in the burn-inrack 140 may independently perform a burn-in on the components loaded onone BIB 112, the chamber slot may begin burn-in of the corresponding BIBas soon as it is delivered to the chamber slot by the BIB transfermodule 120.

Contrasted to conventional burn-in systems where the burn-in chamber andthe BLU are widely separated and the burn-in chamber begins to perform aburn-in process only when all the chamber slots are filled with BIBs,embodiments of the invention provide a significant increase in the UnitsPer Hour per square foot (UPH/ft²) value for the burn-in system.

Referring again to FIG. 2, a trolley 150 may be detachably linked to oneor more of the BIB transfer modules 150. The trolley 150 is used tochange-out BIBs 112 that are circulating within the system 100. Thetrolley 150 may also be used to store an additional supply offunctioning BIBs 112 in case one of the BIBs 112 that is circulatingwithin the system 100 becomes damaged.

For example, a BIB change-out may occur if the system operator wishes tobegin burn-in of components having a different packaging type. Thedifferent packaging type may require a BIB with a different physicalconfiguration. Thus, after a BIB 112 having a first physicalconfiguration is unloaded after a burn-in cycle, the BIB transfer module120 may transfer the BIB to an empty slot in the trolley 150. Then, theBIB transfer module 120 may transfer a BIB 112 having a second physicalconfiguration from another slot in the trolley 150 to the BLU 110.

In this manner, the entire set of BIBs 112 circulating within the system100 may be swapped for a different set of BIBs 112 having a differentphysical configuration. In a similar manner, individual damaged BIBs 112may be exchanged for functioning BIBs 112 stored on the trolley 150 whenthe need arises. According to embodiments of the invention, the BIBs are100% utilized by being self-contained in the linked module burn-insystem.

As illustrated in FIG. 2, in order to transfer the BIBs from the system100 to the trolley 150, the BIB transfer module 120 is capable of movingthe BIB through a 90 degree change of direction. Embodiments of theinvention may accomplish this change of direction through a uniquemechanism that will be explained in further detail below in thedescription of the BIB transfer module 120.

The embodiments of the invention described above provide a system 100including a BLU 110 and a burn-in chamber 130 linked by a BIB transfermodule 120. The system 100 is completely automated. That is, a JEDECtray filled with unburned components is input into the system 100 and aJEDEC tray filled with burned components is received from the system100. Because the system 100 is linked, minimizes the physical footprint,and supports slot-level as opposed to batch-level burn-in, the timerequired for a single BIB to complete a burn-in cycle is substantiallyreduced and the UPH/ft² value is substantially increased compared toconventional burn-in systems. Thus, burn-in systems according toembodiments of the invention are linked module systems capable ofproviding a continuous flow capability to a component burn-in processthat efficiently utilizes chamber time and maximizes the UPH/ft² value.

Maintenance issues are also simplified using embodiments of theinvention. The BIB transfer modules 120 are detachably affixed to theburn-in system 100. That is, the BIB transfer modules 120 may be removedfrom the linked system 100 without disturbing the BLU 110 or the burn-inchamber 130. For example, because the system 100 of FIG. 2 includes twoBIB transfer modules 120, the burn-in system 100 may still function,albeit half as fast, if one of the BIB transfer modules 120 must be shutdown for repairs. Alternatively, a malfunctioning BIB transfer module120 could be replaced by a third spare BIB transfer module 120 andburn-in may resume at full capacity.

Similarly, if individual chamber slots of the burn-in racks 140 becomefaulty, the corresponding BIB transfer module 120 may prevent BIBs frombeing placed in the malfunctioning chamber slot.

FIGS. 3A and 3B are perspective diagrams further illustrating an exampleBIB transfer module 120 from the burn-in system of FIG. 2. The L-shapedBIB transfer module 120 of FIGS. 3A and 3B corresponds to the BIBtransfer module 120 shown linked to the trolley 150 in FIG. 2.

The BIB transfer module 120 includes a BIB transfer mechanism 300, anelevator 310, a vertical buffer 320, and a buffer elevator 340. The BIBtransfer mechanism 300 is attached to the elevator 310, which is capableof raising and lowering the BIB transfer mechanism 300 along the z-axis(vertical axis).

The vertical buffer 320 is attached to the buffer elevator 340, which iscapable of raising and lowering the vertical buffer 320 along the z-axis(vertical axis). The vertical buffer 320 includes buffer rails 350attached to the underside of the vertical buffer. The buffer rails 350are located on opposite sides of the vertical buffer 320 and aligned inthe x-direction. The vertical buffer 320 is capable of reducing andincreasing the horizontal distance between the buffer rails 350, and inthis manner the buffer rails 350 may be closed around the outside edgesof a BIB 112 to suspend the BIB.

The BIB transfer module 120 may also include an access panel 330. Theaccess panel 330 provides a convenient way to access the interior of theBIB transfer module 120 when the BIB transfer module is attached to theBLU 110 and chamber racks 140. There may be other access panels locatedin other positions on the exterior of the BIB transfer module 120.

A trolley 150 is shown attached to the side of the BIB transfer module120. As illustrated in FIGS. 3A and 3B, the BIB transfer module 120 mayalso include wheels 360 that enable the BIB transfer module to be easilypositioned between, attached to, and removed from the BLU 110 and theburn-in chamber 130. The BIB transfer module may also include adjustablefeet 370.

FIGS. 4A, 4B, and 4C are perspective diagrams further illustrating theBIB transfer mechanism 300 of FIGS. 3A and 3B. FIG. 4A is illustrativeof the actuator assemblies that are part of the BIB transfer mechanism300. FIG. 4B is illustrative of the rail assemblies that are part of theBIB transfer mechanism 300. FIG. 4C is illustrative of the actuatorassemblies shown in FIG. 4A and the rail assemblies shown in FIG. 4B, aswell as additional elements not shown in FIG. 4A or 4B.

In order to avoid excessively detailed drawings that might obscureaspects of the invention, FIGS. 4A, 4B, and 4C each show some, but notall, of the components of the BIB transfer mechanism 300. For example,the embodiments of the invention illustrated in FIGS. 4A, 4B, and 4C mayalso include a quantity of electrical wiring to deliver power andcontrol signals, as well as optical sensors to detect the position of aBIB 112. However, because these additional elements are not critical forunderstanding of the invention, they are omitted.

Referring to FIGS. 4A, 4B, and 4C, the BIB transfer mechanism 300includes a lower plate 460, an upper plate 450, a number of chamberrails 410, and a number of z-axis controllable rails 400. The BIBtransfer mechanism 300 also includes two chamber actuator rails 430 andtwo chamber actuators 435 with associated motors 440, and a trolleyactuator rail 420 and trolley actuator 425 with its associated motor440.

As illustrated in FIGS. 4B and 4C, a number of chamber rails 410 areattached along two of the four sides of the lower plate 460. The chamberrails 410 are aligned along the x-axis of the BIB transfer mechanism300. The chamber rails 410 support and guide the BIB 112 when the BIB112 is moved along the x-axis. As is most easily seen in FIG. 4B, eachchamber rail 410 is slightly separated from an adjoining chamber rail410 on the same side of the lower plate 460 by a small gap. The smallgaps between the chamber rails 410 serve an important purpose, as willbe explained in the following paragraphs.

As illustrated in FIGS. 4B and 4C, a number of z-axis controllable rails400 are installed on the lower plate 460. The z-axis controllable rails400 are aligned along the y-axis of the BIB transfer mechanism 300,perpendicular to the chamber rails 410. The z-axis controllable rails400 support and guide the BIB 112 when the BIB 112 is moved along they-axis.

The z-axis controllable rails 400 are also located between the smallgaps formed between the chamber rails 410. The z-axis controllable rails400 may be controlled to be selectively raised in the z-axis (vertical)direction. Because of the small gaps between the chamber rails 410, thez-axis controllable rails may be raised above the horizontal level ofthe chamber rails 410. The z-axis controllable rails 400 may be raisedand lowered along the z-axis by actuators, which are obscured beneaththe lower plate 460. Other BIB transfer mechanisms 300 according toother embodiments of the invention may include more or less z-axiscontrollable rails 400 than the number shown in FIGS. 4B and 4C.

As illustrated in FIGS. 4A and 4C, the BIB transfer mechanism 300 alsoincludes two chamber actuator rails 430 attached to the lower plate 460and two chamber actuators 435 attached to the chamber actuator rails430. For each of the chamber actuators 435 there is a motor 440 thatcontrols the position and movement of the chamber actuators 435 alongthe chamber actuator rails 430 by driving a threaded rod that pushes andpulls the chamber actuators 435 along the chamber actuator rails 430. Arotating finger 470 is located at one end of each of the chamberactuators 435. One of the chamber actuators 435, along with itsassociated chamber actuator rail 430, motor 440, and rotating finger470, may be referred to as a chamber actuator assembly.

According to the illustrated embodiments of the invention, the positionof the rotating finger 470 may be controlled so that in a firstposition, the rotating finger extends above an adjacent upper surface ofcorresponding chamber actuator 435, while in a second position therotating finger 470 is substantially flush with an adjacent uppersurface of the corresponding chamber actuator 435.

An example first position can be seen in FIG. 4A, where the firstchamber actuator 435 that is not engaging the BIB 112 is shown with arotating finger 470 that extends above the adjacent upper surface of thefirst chamber actuator. An example second position may be seen in FIG.4B, where the second chamber actuator 435 is shown with a rotatingfinger 470 that is relatively flush with the adjacent upper surface ofthe second chamber actuator.

When the rotating fingers 470 of the chamber actuators 435 are in thefirst position, they are configured to contact BIB rails (not shown)mounted to the underside of the BIB 112. The rails are aligned in they-direction, perpendicular to the movement of the chamber actuators 435,and located at opposite sides of the BIB 112. The rails provide a pointat which the chamber actuators 435 may use the rotating fingers 470 topush or pull against the BIB 112. Thus, the chamber actuators 435 areable to move the BIB 112 along the x-axis while the BIB is supported bythe chamber rails 410.

The BIB transfer mechanism 300 also includes a trolley actuator rail 420mounted to the upper plate 450 and a trolley actuator 425 attached tothe trolley actuator rail 420. The trolley actuator rail 420 is attachedto the underside of the lower plate 450, which is why the trolleyactuator rail 420 cannot be seen in FIG. 4C. In order for the trolleyactuator rail 420 and trolley actuator 425 to be completely illustrated,they are shown in FIG. 4A in a “floating” position, without the upperplate 450 to which the trolley actuator rail 420 is attached. For thetrolley actuator 425 there is a motor 440 that controls the position andmovement of the trolley actuator 425 along the trolley actuator rail 420by driving a threaded rod that pushes and pulls the trolley actuator 425along the trolley actuator rail 420. A rotating finger 470 may belocated at one end of the trolley actuator 425. The trolley actuator425, along with its associated trolley actuator rail 420, motor 440, androtating finger 470, may be referred to as a trolley actuator assembly.

According to the illustrated embodiments of the invention, the positionof the rotating finger 470 may be controlled so that in a firstposition, the rotating finger extends below the adjacent lower surfaceof the trolley actuator 425, while in a second position the rotatingfinger 470 is substantially flush with the adjacent lower surface of thetrolley actuator 425. In FIG. 4A, the trolley actuator 425 is shown witha rotating finger 470 that is in the second position. If the rotatingfinger 470 of the trolley actuator 435 were in the first position, itwould exhibit a position similar to the rotating finger 470 of thechamber actuator 435 shown in FIG. 4A, except of course extendingdownwards rather than upwards.

According to the illustrated embodiments of the invention, when therotating finger 470 of the trolley actuator 425 is in the firstposition, it is configured to contact BIB rails 113 that are attached tothe top side of the BIB 112. The BIB rails 113 are aligned in thex-direction, perpendicular to the movement of the trolley actuator 425,and located at opposite sides of the BIB 112. The BIB rails 113 providea point at which the trolley actuator 425 may use the associatedrotating finger 470 to push or pull against the BIB 112. Thus, thetrolley actuator 425 is able to move the BIB 112 along the y-axis whilethe BIB is being supported by the z-axis controllable rails 400.

According to the illustrated embodiments of the invention, the BIB rails113 are aligned in the x-direction on opposite sides of the BIB 112,while the BIB rails (not shown) on the underside of the BIB 112 arealigned in the y-direction. Because the BIB 112 is rectangular, the BIBrails 113 may be shorter than the BIB rails (not shown) on the undersideof the BIB 112.

It is preferable that the BIB 112 include some sort of structuralmember, other than the sockets that hold the components, forthe-rotating fingers 470 of the chamber actuator assemblies and thetrolley actuator assembly to interface with. In the illustratedembodiments of the invention, these structural members are the BIB rails113. In alternative embodiments of the invention, the length of the BIBrails 113 may be different. For example, the BIB rails 113 may be justlong enough to contact the rotating finger 470 of the trolley actuatorassembly. Similarly, in alternative embodiments of the invention, thelength of the BIB rails (not shown) on the underside of the BIB 112 maybe just long enough to contact the rotating fingers 470 of the chamberactuator assembly. In still other embodiments of the invention, therotating fingers 470 may instead be designed to interface with recessedslots or holes in the surface of the BIB 112, or some other structuralmember that protrudes from the surface of the BIB 112.

The trolley actuator rail 420 is arranged perpendicularly with respectto the chamber actuator rails 430. The trolley actuator assemblyfacilitates movement of the BIB 112 in the y-direction, while thechamber actuator assemblies facilitate movement of the BIB 112 in thex-direction. It should be apparent that in other embodiments of theinvention, the z-axis controllable rails 400 and the trolley actuatorassembly may be arranged to facilitate movement of the BIB 112 in thex-direction, while the chamber rails 410 and the chamber actuatorassemblies facilitate movement of the BIB 112 in the y-direction.

According to the embodiments illustrated above, the BIB transfermechanism 300 is capable of moving the BIB 112, using the chamberactuator assemblies, to a position adjacent to either side of the BIBtransfer mechanism 300 in the x-direction. The maximum distance that theBIB 112 may be moved away from the BIB transfer mechanism will dependupon the overall length of the chamber actuator 435 and the maximumdisplacement position of the chamber actuator 435 along thecorresponding chamber actuator rail 430.

As illustrated in FIG. 4A, the BIB 112 is shown fully extended away fromthe BIB transfer mechanism 300 in the positive x-direction. This is theposition where the chamber rack 140 of FIG. 2 would be located. As shownin FIG. 3, the BIB transfer mechanism 300 is attached to the elevator310. The height of the BIB transfer mechanism 300 may be easilyadjusted, using the elevator 310, so that as the BIB 112 is moved off ofthe chamber rails 410 by the chamber actuator assembly, the BIB 112slides easily into the selected chamber slot of the chamber rack 140.Each chamber slot has its own rails (not shown) that are capable ofsupporting the BIB 112.

Similarly, the other chamber actuator assembly of FIG. 4A may be used toextend the BIB 112 away from the BIB transfer mechanism 300 in thenegative x-direction. This position corresponds to where the transferbetween the BIB transfer mechanism 300 and the vertical buffer 320 (FIG.3A) occurs.

According to the illustrated embodiments of the invention, the BIBtransfer mechanism 300 is capable of moving the BIB 112, using thetrolley actuator assembly, to a position adjacent to one side of the BIBtransfer mechanism 300 in the negative y-direction. The maximum distancethat the BIB 112 may be moved away from the BIB transfer mechanism willdepend upon the overall length of the trolley actuator 425 and themaximum displacement position of the trolley actuator 425 along thetrolley actuator rail 420.

The position adjacent to one side of the BIB transfer mechanism 300 inthe negative y-direction corresponds to the position where the trolley150 of FIG. 2 would be located. As shown in FIG. 3, the BIB transfermechanism 300 is coupled to the elevator 310. The height of the BIBtransfer mechanism 300 may be easily adjusted, using the elevator 310,so that as the BIB 112 is moved off of the z-axis controllable rails 400by the trolley actuator assembly, the BIB 112 slides easily into one ofthe selected open positions of the trolley 150. As illustrated in FIGS.3A and 3B, each trolley 150 has a number of pairs of rails, each pair ofrails arranged vertically above or below the other, each pair of railscapable of supporting the BIB 112.

According to the illustrated embodiments of the invention, the BIBtransfer mechanism 300 may move the BIB 112 in the positive x-directionor the negative x-direction when the BIB 112 is supported by the chamberrails 410. Similarly, the BIB transfer mechanism may move the BIB 112 inthe positive y-direction or the negative y-direction when the BIB 112 issupported by the z-axis controllable rails 400.

According to the illustrated embodiments of the invention, when thez-axis controllable rails 400 are raised above the level of the chamberrails 410, a BIB 112 that is positioned on the chamber rails 410 islifted from the chamber rails 410 by the z-axis controllable rails 400.The BIB 112 is lifted sufficiently high so that the rotating finger 470of the trolley actuator assembly may engage the BIB rails 113, allowingthe BIB transfer mechanism 300 to push and/or pull the BIB 112 along they-axis.

Conversely, when the z-axis controllable rails 400 are positioned belowthe level of the chamber rails 410, the BIB 112 is supported by thechamber rails 410 and not by the z-axis controllable rails 400.Preferably, when the BIB 112 is supported by the chamber rails 410, onlythe rotating fingers 470 of the chamber actuator assemblies may engagethe BIB rails (not shown) on the underside of the BIB 112, allowing theBIB transfer mechanism 300 to push and/or pull the BIB 112 along thex-axis.

Thus, according to the embodiments of the invention described above, aBIB transfer module 120 may easily move a BIB 112 in perpendiculardirections while minimizing the required physical footprint by using theBIB transfer mechanism 300. In other words, the BIB transfer mechanism300, which has a physical footprint that is equal to only about the areaof one BIB, may position a BIB adjacent to the BIB transfer mechanism inthree directions through utilization of the chamber actuator assembliesand the trolley actuator assembly.

According to alternative embodiments of the invention, the BIB transfermechanism 300 of FIGS. 4A, 4B, and 4C may include a second trolleyactuator assembly. This would allow the BIB transfer mechanism 300 tomove a BIB 112 away from the BIB transfer mechanism in the positivey-direction. Although such a configuration for the BIB transfermechanism 300 would not be useful for the burn-in system 100 illustratedin FIG. 2, these embodiments may be useful in other burn-in systemswhere the BLU 110, the BIB transfer module 120, and the burn-in chamber130 have different physical footprints.

In the embodiments illustrated above, chamber rails 410 and z-axiscontrollable rails 400 are used to guide and support the BIB 112 as itis moved along the x-axis and the y-axis, respectively. However, otherembodiments of the invention may utilize structures other than rails,although rails are preferred.

For example, a BIB transfer mechanism according to alternativeembodiments of the invention may have a number of posts with smallwheels attached to the top of the posts. The axis of rotation of some ofthe wheels may be parallel to the x-axis, while the axes of rotation ofother wheels may be parallel to the y-axis. The posts having wheels withaxes of rotation parallel to the x-axis would therefore rotate to enablemovement parallel to the y-axis, and the posts having wheels with axesof rotation parallel to the y-axis would rotate to enable movementparallel to the x-axis.

One set of posts, for example, the set of posts having wheels with axesof rotation parallel to the x-axis, may be structured such that theirvertical height is adjustable with respect to the set of posts havingwheels with axes of rotation parallel to the y-axis. Thus, the set ofposts that have an adjustable vertical height is functionally similar tothe z-axis controllable rails 400 of the embodiments illustrated above.The set of posts that do not have an adjustable vertical height isfunctionally similar to the chamber rails 410 of the embodimentsillustrated above.

In these alternative embodiments of the invention, when the BIB issupported by a particular set of posts, the wheels on the posts may bestructured to roll along corresponding grooves on the underside of theBIBs that are arranged parallel to the x-axis or parallel to the y-axis.Or, the wheels on the posts may be structured to roll alongcorresponding gaps formed between adjacent BIB rails that are attachedto the underside of the BIBs.

To provide an overall understanding of the above-described embodimentsof the invention, an example route for one BIB 112 as it moves throughthe burn-in system 100 of FIG. 2 will be briefly described below, withreference to FIGS. 2, 3, and 4.

During operation of the burn-in system 100, a JEDEC tray 114 filled withunburned components is loaded in the BLU 110. The BLU 110 unloads theunburned components from the JEDEC tray 114 and places them on an emptyBIB 112 which is circulating within the burn-in system 100. The BLU 110may then place the BIB 112 beneath the vertical buffer 320 of the BIBtransfer module 120.

The vertical buffer 320 is capable of moving along the z-axis (verticalaxis) as well as along the x-axis. The vertical buffer 320 may belowered to be placed in close proximity with the BIB 112. The verticalbuffer 320, by adjusting the distance between the buffer rails 350 andthe vertical distance to the BIB 112, may control the buffer rails 350so that they support the BIB and raise it from the supporting surface ofthe BLU 110. Next, the vertical buffer 320 may move the BIB 112 in thepositive x-direction, positioning the BIB so that it is located adjacentto the BIB transfer mechanism 300.

Using one of the two chamber actuator assemblies that was describedabove, the BIB transfer mechanism 300 engages a BIB rail (not shown)that is attached to the underside of the BIB 112 with the rotatingfinger 470, and pulls the BIB 112 onto the chamber rails 410, towardsthe center of the BIB transfer mechanism 300, in the positivex-direction. Once the BIB 112 is within the boundaries of the BIBtransfer mechanism 300, the BIB transfer mechanism may be moved in thepositive or negative z-direction so that the upper surfaces of thechamber rails 410 are substantially even with the upper surfaces of theselected chamber slot in the attached chamber rack 140.

At some point, the first chamber actuator assembly is unable to pull theBIB 112 any further in the positive x-direction, and the second of thetwo chamber actuator assemblies engages the other BIB rail (not shown)that is attached to the underside of the BIB 112 with the rotatingfinger 470. The second chamber actuator assembly is then able to pushthe BIB 112 from off of the chamber rails 410 and into the selectedchamber slot of the chamber rack 140 so that the BIB 112 may beconnected to the electrical contacts that are present with the chamberslot. The burn-in process for the BIB 112 may then begin.

After the burn-in process is finished, the baked components on the BIB112 may be transferred to a JEDEC tray 114 after the BIB 112 is unloadedfrom the chamber rack 140 by performing substantially the reverse of theabove-described processes.

According to the above embodiments of the invention, BIBs 112 that arecirculating within the system may also be quickly and easily swapped forother BIBs with the aid of a conventional trolley that is detachablyaffixed to the BIB transfer module 120.

To further provide an overall understanding of the above-describedembodiments of the invention, an example route for one BIB 112 as it isswapped out of the system will be described with reference to FIGS. 2,3, and 4. In the following description, a BIB 112 that is to be placedinto the burn-in system 100 will be referred to as “new,” while a BIB112 that is to be removed from the burn-in system 100 will be referredto as “old.”

A conventional trolley 150, loaded with new BIBs 112, may be attached toone side of the BIB transfer module 120, as illustrated in FIG. 2. Theelevator 310 may be used to adjust the height of the BIB transfermechanism 300 so that the trolley actuator assembly is capable ofengaging a BIB rail 113 of a selected BIB 112 that is loaded on thetrolley 150 with the rotating finger 470.

The BIB transfer mechanism 300 activates the z-axis controllable rails400 so that they rise above the upper surfaces of the chamber rails 410.The height of the z-axis controllable rails 400 is controlled so that anupper surface of the z-axis controllable rails 410 is substantiallylevel with an upper surface of a rail that supports the selected BIB 112in the trolley 150.

Once the z-axis controllable rails 400 are in place, the trolleyactuator assembly pulls the selected BIB 112 from the trolley and ontothe z-axis controllable rails 400. At the appropriate position of theBIB 112, the z-axis controllable rails 400 are lowered beneath the uppersurface of the chamber rails 410, allowing the BIB 112 to be supportedby the chamber rails.

If necessary, the elevator 310 moves the BIB transfer mechanism 300,along with the selected BIB 112, to a height corresponding to thevertical buffer 320. Next, the BIB transfer mechanism slides the BIB 112off of the chamber rails 410 and onto the buffer rails 350 of thevertical buffer 320 using a chamber actuator assembly. Next, thevertical buffer 320, by adjusting the distance between the buffer rails350 and the vertical distance to the BLU 110, may place the new BIB 112on the supporting surface of the BLU 110.

The BLU 110 moves an old BIB 112 to where it can be picked up by thevertical buffer 320, and by following processes substantially thereverse of those described above the old BIB 112 is placed in acorresponding empty position of the trolley 150 using the BIB transfermodule 120.

Using the processes described above, a burn-in system 100 according tothe illustrated embodiments of the invention exhibit a marked increasedin the UPH/ft² value compared to conventional burn-in systems. Thisincrease is attributable to the fact that the illustrated embodiments ofthe invention support slot-level burn-in, and that the BLU 110 andburn-in oven 120 are no longer widely separated.

For example, once the BLU 110 delivers a BIB 112 with unbaked componentsto the first BIB transfer module 120, it may immediately deliver anotherBIB 112 with unbaked components to the second BIB transfer module 120.The BIB transfer modules 120 may then transfer the BIBs 112 with unbakedcomponents to an unoccupied chamber slot in the corresponding chamberrack 140. Once the BIB 112 is loaded in the chamber slot, the burn-inprocess for the unbaked components on the BIB 112 may begin.

The BIB transfer modules 120 may then immediately pick up another BIB112 loaded with unbaked components and load the BIB into thecorresponding chamber rack 140. Alternatively, the BIB transfer modules120 may first remove a BIB 112 that has completed the burn-in cycle fromits chamber slot and return it to the BLU 110 before receiving the nextBIB 112 with unbaked components.

A typical chamber rack 140 may contain, for example, 16 chamber slots.Assuming that the illustrated BIB transfer module 120 began filling achamber rack 140 having 16 initially empty chamber slots, a BIB 112loaded in the topmost chamber slot would complete the burn-in cycle wellbefore the lowermost chamber slot could be filled. Thus, the BIBtransfer module 120 would soon begin, in each round trip, delivering aBIB 112 with unbaked components to the chamber rack 140 and returning aBIB 112 with baked components to the BLU 110 for repackaging on a JEDECtray.

The preceding embodiments are exemplary. Those of skill in the art willrecognize that the concepts taught herein can be tailored to aparticular application in many other advantageous ways. In particular,those skilled in the art will recognize that the illustrated embodimentsare but one of many alternative implementations that will becomeapparent upon reading this disclosure.

Although the specification may refer to “an”, “one”, “another”, or“some” embodiment(s) in several locations, this does not necessarilymean that each such reference is to the same embodiment(s), or that thefeature only applies to a single embodiment.

Many of the specific features shown herein are design choices. Thenumber and type of JEDEC trays, the number and type of BIBs, the numberof BIB transfer modules, the number of BLUs, and the number of burn-inchambers are all merely presented as examples. For instance, in theexemplary embodiments described above a single BLU was linked to twoburn-in chambers by two BIB transfer modules. However, it should beapparent that in other embodiments of the invention a single BLU may beconnected to a single burn-in chamber, or a BLU could be connected tothree or more burn-in chambers by a corresponding number of BIB transfermodules.

Likewise, functionality embodied in a single module or functional blockof the burn-in system may be implemented using multiple cooperatingcircuits or blocks, or vice versa. For example, the BIB transfer modulesdescribed above may be separated from the BLU unit. However, accordingto other embodiments of the invention the BIB transfer module may forman integral part of the BLU unit. Such minor modifications areencompassed within the embodiments of the invention, and are intended tofall within the scope of the attached claims.

1. A system comprising: a first burn-in board (BIB) structured to hold afirst plurality of components; a first burn-in chamber rack with a firstchamber slot, the first chamber slot structured to hold the first BIB; aBIB loader/unloader (BLU) structured to load the first plurality ofcomponents on the first BIB and structured to remove the first pluralityof components from the first BIB; and a first BIB transfer modulelinking the BLU to the first burn-in chamber rack, the first BIBtransfer module structured to transfer the first BIB between the BLU andthe first chamber slot by moving the first BIB in directions parallel toat least two axes of a coordinate system having three mutuallyperpendicular axes.
 2. The system of claim 1, further comprising: asecond BIB structured to hold a second plurality of components, whereinthe BLU is structured to load the second plurality of components on thesecond BIB and structured to remove the second plurality of componentsfrom the second BIB; a second burn-in chamber rack with a second chamberslot, the second chamber slot structured to hold the second BIB; and asecond BIB transfer module structured to couple to the BLU and thesecond burn-in chamber rack, the second BIB transfer module configuredto transfer the second BIB between the BLU and the second chamber slotby moving the second BIB in directions parallel to at least two axes ofthe coordinate system.
 3. The system of claim 1, further comprising: afirst trolley structured to couple to the first BIB transfer module andhaving a first trolley slot structured to hold the first BIB, whereinthe first BIB transfer module is structured to transfer the first BIBfrom one chosen from a group consisting of the BLU, the first chamberslot, and the first trolley slot to another one chosen from the group bymoving the first BIB in directions parallel to at least two axes of thecoordinate system.
 4. The system of claim 2, further comprising: asecond trolley structured to couple to the second BIB transfer moduleand having a second trolley slot structured to hold the second BIB,wherein the second BIB transfer module is structured to transfer thesecond BIB from one chosen from a group consisting of the BLU, thesecond chamber slot, and the second trolley slot to another one chosenfrom the group by moving the second BIB in directions parallel to atleast two axes of the coordinate system.
 5. The system of claim 2, thefirst BIB transfer module structured to be detached from the BLU and thefirst burn-in chamber rack while the second BIB transfer module istransferring the second BIB between the BLU and the second chamber slot.6. The system of claim 5, the first BIB transfer module comprisingwheels attached to the bottom of the first BIB transfer module.
 7. Thesystem of claim 1, the BLU further structured to transfer the firstplurality of components between the first BIB and a JEDEC tray.
 8. Thesystem of claim 2, the system structured to provide a continuous flowcapability for a component burn-in process that efficiently utilizes thefirst burn-in chamber rack and second burn-in chamber rack and maximizesthe UPH/ft² value.
 9. A system comprising: a first burn-in board (BIB)transfer module structured to connect a BIB Loader/Unloader (BLU) to afirst burn-in chamber rack, the first BIB transfer module structured totransfer a first burn-in board (BIB) between the BLU and the firstburn-in chamber rack by moving the first BIB in directions parallel toat least two axes of a coordinate system having three mutuallyperpendicular axes.
 10. The system of claim 9, further comprising: asecond BIB transfer module structured to connect the BLU to a secondburn-in chamber rack, the second BIB transfer module structured totransfer a second BIB between the BLU and the second burn-in chamberrack by moving the second BIB in directions parallel to at least twoaxes of the coordinate system.
 11. The system of claim 9, wherein thefirst BIB transfer module is structured to be detachably affixed to atrolley, the first BIB transfer module further structured to transferthe first BIB from one chosen from the group consisting of the BLU, thefirst burn-in chamber rack, and the trolley to another one chosen fromthe group consisting of the BLU, the first burn-in chamber rack, and thetrolley by moving the first BIB in directions parallel to at least twoaxes of the coordinate system.
 12. The system of claim 10, wherein thesecond BIB transfer module is structured to be detachably affixed to atrolley, the second BIB transfer module further structured to transferthe second BIB from one chosen from the group consisting of the BLU, thesecond burn-in chamber rack, and the trolley to another one chosen fromthe group consisting of the BLU, the second burn-in chamber rack, andthe trolley by moving the second BIB in directions parallel to at leasttwo axes of the coordinate system.
 13. The system of claim 12, the firstBIB transfer module structured to be detached and separated from the BLUand the first burn-in chamber rack while the second BIB transfer moduleis transferring the second BIB.
 14. The system of claim 13, the firstBIB transfer module comprising wheels attached to the bottom of thefirst BIB transfer module.
 15. A method comprising linking at least twomodules of a burn-in system to each other with a transfer module toenable slot-level burn-in of components and to maximize a Units Per Hourper square foot (UPH/ft²) value of the burn-in system.
 16. The method ofclaim 15, wherein linking at least two modules of a burn-in system toeach other with a transfer module comprises: linking a Burn-In Board(BIB) Loader/Unloader (BLU) to a first burn-in chamber rack with a firstBIB transfer module; and transferring a first BIB from one of the BLUand the first burn-in chamber rack to another one of the BLU and thefirst burn-in chamber rack using the first BIB transfer module.
 17. Themethod of claim 16, further comprising: linking the BLU to a secondburn-in chamber rack with a second BIB transfer module; and transferringa second BIB from one of the BLU and the second burn-in chamber rack toanother one of the BLU and the second burn-in chamber rack using thesecond BIB transfer module.
 18. The method of claim 16, furthercomprising: attaching a trolley to the first BIB transfer module; andtransferring the first BIB from one chosen from the group consisting ofthe BLU and the first burn-in chamber rack to the trolley using thefirst BIB transfer module.
 19. The method of claim 18, whereintransferring the first BIB comprises moving the first BIB in directionsparallel to at least two axes of a coordinate system having threemutually orthogonal axes.
 20. The method of claim 17, further comprisingdetaching and separating the first BIB transfer module from the BLU andthe first burn-in chamber rack while the second BIB is being transferredwith the second BIB transfer module.
 21. The method of claim 20, whereindetaching and separating comprises moving the first BIB transfer moduleaway from the BLU and the first burn-in chamber rack using wheelsaffixed to the bottom of the first BIB transfer module.
 22. The methodof claim 18, further comprising transferring a second BIB from thetrolley to one chosen from the group consisting of the BLU and the firstburn-in chamber rack using the first BIB transfer module.